Derivation of constants used in x86_64 libmvec implementation

[Bert Tenjy <bert dot tenjy at gmail dot com>]

The comments at the top of several assembly files states "...The table 
may contain polynomial, reduction, lookup coefficients obtained through 
different research and experimental work."

Any pointers at more specific literature that would assist in deriving 
these constants will be much appreciated.

To be specific, deriving the following and other similar constants in 
sysdeps/x86_64/fpu/svml_d_trig_data.S, is the information being sought:

__dPI1_FMA, __dPI2_FMA, __dPI3_FMA,__dC1,__dC1_sin,__dRShifter_la

Thanks.
Bert Tenjy.